The cooling system is essential for proper operation of vehicles of many types. Particularly, large trucks (e.g., medium- or heavy-duty trucks) rely heavily on the cooling system for optimum operation and the protection of the vehicle from overheating.
Because of the complexity of the cooling systems in large trucks, special manufacturing techniques have been developed to fill the cooling system with coolant for operation. Vacuum filling is a particularly useful technique, wherein a vacuum (e.g., 20 torr) is applied to a closed cooling system and coolant is then flushed into the evacuated cooling system. Vacuum filling helps to eliminate detrimental effects, such as trapped air pockets, which arise during traditional filling (e.g., non-vacuum) of a vehicular cooling system.
While vacuum filling of vehicular cooling systems can lead to increased efficiency when charging new vehicular cooling systems with coolant within a manufacturing plant, the vacuum filling technique is not without drawbacks. Particularly, the relatively high vacuum required for the method can lead to stress, strain, and possibly structural failure, of the individual components of the cooling system.
One particular component of a vehicular cooling system that is susceptible to structural failure when subjected to the high vacuum pressures of vacuum coolant filling is the coolant reservoir, which is the entry point for coolant into a vehicular cooling system. The coolant reservoir is traditionally manufactured from an inexpensive and lightweight material, such as blow-molded plastic. Such a plastic is not structurally sufficient to withstand the relatively high vacuum of the vacuum filling technique described above, and rupture of the coolant reservoir may result.
One potential solution to the structural susceptibility to failure of the coolant reservoir is to manufacture the reservoir from a more robust material, such as metal, that would withstand the applied vacuum pressures. However, the coolant reservoir is not a vital component in the cooling system and, after charging of the cooling system with coolant, the coolant reservoir is used very lightly, and only under standard temperatures and pressures (i.e., the coolant reservoir does not need to withstand further vacuum pressures after the cooling system has been charged with coolant). Thus, investing additional manufacturing cost into designing, implementing, and manufacturing a more robust coolant reservoir is not a financially viable option for a manufacturer because significant additional cost would be invested for a benefit that is not passed on to the end customer. For example, a customer does not require a metallic coolant reservoir and would not likely want to pay a premium for such a component when its only benefit is to allow the manufacturer to use a vacuum coolant filling process.
A second option for overcoming the structural failure of the coolant reservoir during vacuum filling is to remove the coolant reservoir prior to vacuum filling. However, during a typical large-truck manufacturing process, the coolant reservoir is attached to the cooling system prior to the step of charging the cooling system with coolant. Thus, for the coolant reservoir to be removed prior to charging of the cooling system, additional labor and inefficiencies would be generated when detaching the coolant reservoir, filling the cooling system, and then reattaching the coolant reservoir.
What is desired, therefore, is a practical solution that would allow for vacuum filling of a cooling system with coolant that allows manufacturers to continue to use inexpensive (e.g., blow-molded polymer) coolant reservoirs while taking full advantage of the vacuum coolant filling technique. And to perform such an action in the typically small amount of time allotted on a production line for filling a cooling system (e.g., less than 5 minutes).